QCD Predictions for Lepton Spectra in Inclusive Heavy Flavour Decays
I. I. Bigi, M. Shifman, N. G. Uraltsev, A. Vainshtein
TL;DR
The lepton spectrum in semileptonic [ital b] decays is derived from a nonperturbative treatment of QCD; it is based on an expansion in 1/[ital m][sub [ital Q]][sup 2] terms with [ital m] being the heavy flavor quark mass.
Abstract
We derive the lepton spectrum in semileptonic beauty decays from a nonperturbative treatment of QCD; it is based on an expansion in $1/m_Q$ with $m_Q$ being the heavy flavour quark mass. The leading corrections arising on the $1/m_Q$ level are completely expressed in terms of the difference in the mass of the heavy hadron and the quark. Nontrivial effects appear in $1/m_Q^2$ terms affecting mainly the endpoint region; they are different for meson and baryon decays as well as for beauty and charm decays.